Silent Power: Fanless PSU Roundup

I am sure that anyone would love to have a quiet power supply unit in their system. The products addressing these wishes are the fanless PSU models, which have no noise-making components by definition. Today we are going to talk about four products like that from Enhance, Kingwin, Seasonic and Silverstone.

by Dmitry Vasiliev
04/08/2012 | 04:09 AM

Fanless power supply units are paradoxically both innovative and conservative products. On one hand, they have to have the most advanced circuit design available at the moment to ensure highest efficiency possible because the less power is dissipated as heat, the more power can be transferred to the computer components. But on the other hand, once they are released, such products stay on the assembly line for a very long time. Why? Well, their advanced components are expensive, the high price limiting the target audience. And there are fewer competitors in this market sector as opposed to ordinary PSUs, so no one feels obliged to hurry up with the development and production of new models.


Indeed, we've got both innovative and conservative products for this review. We’ve known the Silverstone Nightjar and the fanless Seasonic X-Gold series for a few years already whereas the PSUs from Kingwin and Enhance are newcomers released in 2011.

Let’s see if the newer products are any better than the older ones, in the order of ascending wattage.

Testing Methodology

The following article offers a detailed description of our testing methodology and equipment and a brief explanation of what the specified and tested parameters of power supplies mean: X-bit Labs Presents: Power Supply Units Testing Methodology. If you feel overwhelmed with the numbers and terms this review abounds in, refer to the Methodology.

You can also go to our Cases/PSU section to check out reviews of all other PSU models we have tested in our labs.

We will mark the actual power consumption of three system configurations (discussed in our article PC Power Consumption: How Many Watts Do We Need?) in the cross-load diagrams. This will help you see if the tested PSU can meet the requirements of a real-life PC.

Testing Participants

Enhance ATX-0340N 400W

Enhance hasn’t been counted among the few makers of silent PSUs until recently. The company unveiled its first such products from the ATX0300N series at Computex 2011.

Currently, this series includes two models: the 300-watt ATX-0330N and the 400-watt ATX-0340N. We’ve got the latter model for us to test.

Exterior Design

The fanless PSU from Enhance doesn’t look like a typical product of its class that would have an aluminum top propped by huge heatsinks. It resembles Seasonic’s silent PSUs in this respect.

The ATX-0340N is almost weightless thanks to the lack of a massive heat-spreading top. Every panel of the case is perforated for ventilation.

Even the bottom panel is meshed, although there’s a layer of insulation material between it and the PCB.

There are an On/Off switch and a tiny label with product specs on the external panel of the PSU.

Circuit Design

The ATX-0340N doesn’t resemble Seasonic's products on the inside. Its black heatsinks are bigger and cover most of the PSU’s internals, making it hard to see the components. We avoid taking PSUs apart during our tests.

So, we can only see DC-DC converters with slim aluminum plates as heatsinks. That’s a solution one can expect to find in a modern fanless PSU.

We can also make out a supervisor chip PS232S through the perforated panel.

There are at least three brands of capacitors on the PSU’s output.

While Teapo components are largely blameless, Taicon and Su’scon do not enjoy such a good reputation.

Besides that, there are reputable United Chemi-Con capacitors in this PSU, although not in the output circuitry. We can’t but wonder why Enhance preferred to install worse components at the output.

Cables and Connectors

The Enhance ATX-0340N is equipped with the following cables:

The short cables imply that the ATX-0340N is targeted at mini-ITX system cases compatible with standard PC components such as Lian Li PC-Q7 or PC-Q11. Considering this positioning, we can hardly blame the PSU for its having short cables with very few connectors. However, you should keep it in mind that the cables are going to be too short for a full-size system case, especially with a bottom PSU bay.

The odd design of the 4+4-pin connector on the CPU power cable can hardly be explained even by the mini-ITX positioning. We don't know the purpose of the additional stretch of the cable with the second half of the connector (it cannot serve as a kind of extension card for mainboards with a 4-pin CPU power connector because it's the first half of the connector that is plugged in in that case).


You can read the product specs from the small and rather untidy label next to the mains connector. There is just no other place for it on the perforated surface of the case.

The combined load capacity of the two +12V lines is not specified but we used a load of 369 watts, or 99% of the PSU’s full output power, in our test, similar to the other products in this review.

The rest of the specs are typical enough for a modern PSU: up to 120 watts on the +3.3V and +5V rails combined and up to 2.5 amperes on the standby source.

This series of PSUs from Enhance is certified to comply with the 80 PLUS Silver standard.

UPS Compatibility

Working together with our APC SmartUPS SC 620, this PSU was stable at loads up to 392 watts when powered by the mains and could switch to the UPS’s batteries at loads up to 305 watts.

Cross-Load Voltage Stability

The +12V and +5V voltages are simply immaculate and never deflect from their required levels by more than 2%. There is an anomaly in the zone of low loads, but it's due to a different voltage.

The +3.3V line doesn’t behave well. Its voltage is too high at low loads, exceeding the permissible range even.

This must be a defect of the particular sample of the PSU. It’s hard to believe that one voltage can be that worse than the others in a PSU with dedicated voltage regulation.

Output Voltage Ripple

The output voltage ripple is rather strong, but meets the industry requirements.

The same goes for the voltage ripple at the double frequency of the mains.

Efficiency and Power Factor

At the reference loads of 20%, 50% and 100%, the Enhance ATX-0340N was 85.7%, 89.6% and 90.5% efficient. It is an 80 PLUS Silver unit indeed. It doesn’t meet the Gold requirements at low and medium loads but its efficiency is actually as high as Platinum at the maximum load.

The peak efficiency of 91.4% was achieved at a load of 268 watts.

The power factor is about 97%, which is somewhat lower than the most efficient implementations of active power factor correction.

Standby Source

The standby source copes with its job, always staying within 0.1 volts of the required level.


The Enhance ATX-0340N is an interesting option for compact system cases but our impression was somewhat spoiled by its +3.3V voltage which is too far off the required level in the typical load range.

Seasonic SS-460FL (X-460 Fanless)

This PSU is the more advanced of the two fanless products produced by Seasonic (we reviewed its junior cousin a year and a half ago).

This model comes in Seasonic's Gold series packaging.

The accessories include fasteners, a few cable straps, some documentation, and a Seasonic sticker for your system case.

The cables and the PSU are packed individually.

Exterior Design

The SS-460FL looks identical to its 400-watt cousin we’ve tested already.

The all-modular design of this PSU differentiates it from most other fanless products.

There’s a label with electrical specs on the bottom of the PSU. The external panel is embellished with a manufacturer’s plaque.

There’s a reminder for you that the PSU must be positioned in the system case with the vent grid facing up.

Circuit Design

The SS-460FL having rather small heatsinks even compared to actively cooled PSUs, we can have a better view of its internals. However, we can't add anything new to what we wrote in our review of the 400-watt cousin of this model.

The PSU employs capacitors from United Chemi-Con and Rubycon.

Cables and Connectors

The Seasonic SS-460FL is an all-modular PSU that comes with the following cables:

There are four PATA/SATA power cables for the PSU’s three connectors so that you could flexibly choose the cables you need for your particular PC configuration.

The selection of connectors is up to the PSU’s wattage and the cables are long enough even for large system cases with a bottom PSU compartment.


The specs are up to today’s requirements. The PSU can deliver almost all of its output power across the +12V rail. The load capacity of the other rails is rather low, yet about twice the needs of a typical computer.

The SS-460FL is 80 PLUS Gold certified.

UPS Compatibility

Working with our APC SmartUPS SC 620, this PSU was stable at loads up to 415 watts when powered by the mains but could only switch to the UPS's batteries at loads up to 292 watts.

Cross-Load Voltage Stability

The +12V voltage is never more than 3% off the required level. This 3% deflection only occurs when the computer is idle.

The +5V voltage is even better, never deflecting by more than 2%.

The +3.3V voltage is the least stable of all. Fortunately, it doesn’t go out of the permissible range, as that of the the above-discussed Enhance, but can be 4% off at low loads.

Output Voltage Ripple

Seasonic’s PSUs have always been good in this test, and this model is no exception.

The high-frequency voltage ripple is very weak, especially on the +12V rail.

The voltage ripple at the frequency of 2 milliseconds is weak as well.

Efficiency and Power Factor

At the reference loads of 20%, 50% and 100%, the Seasonic SS-460FL is 88.1%, 91.8% and 92.1% efficient. This complies with the 80 PLUS Gold requirements the PSU is certified for.

The peak efficiency of 93.4% was achieved at a load of 270 watts.

The power factor is about 97% at high loads, which is somewhat lower than the best implementations of active power factor correction.

Standby Source

The standby source is okay, its voltage never being more than 2% off the required level.


The Seasonic SS-460FL is in fact blameless, save for its indecent price. Its +3.3V voltage might be more stable, yet it's always within the required range anyway.

Silverstone Nightjar SST-ST50NF

Kingwin is supposed to be next alphabetically, but there is one nuance in its specs that makes us choose this order of presentation. So, next goes Silverstone Nightjar SST-ST50NF.

The PSU comes in a rather large box that lacks a carry handle. The smaller box of its 450-watt predecessor we tested earlier had one.

Exterior Design

The Nightjar SST-ST50NF looks like a typical fanless PSU with its massive aluminum heat-spreading top and meshed side panels.

As opposed to the Enhance, the bottom panel is blank. The Nightjar SST-ST50NF also differs from the Seasonic as it has not a single modular cable.

The case of the PSU is all made of aluminum, which is a questionable solution. Aluminum makes the end product more expensive but contributes little to cooling the PSU’s components.

Like its 450-watt cousin, the 500-watt Nightjar SST-ST50NF has power and temperature indicators on the back panel. The Power indicator is orange rather than green and may be confused for a warning signal at first sight.

Circuit Design

The top panel has contact with the internal heatsink via thermal pads.

Like its junior cousin, the Nightjar SST-ST50NF has massive heatsinks covering most of its interior.

Some characteristic details indicate that this PSU shares the hardware platform with the 450-watt model from the same series.

The PSU has four input capacitors instead of the conventional one or two. There are two daughter cards with controller chips nearby.

The Nightjar SST-ST50NF employs electrolytic capacitors from United Chemi-Con.

Cables and Connectors

The Nightjar SST-ST50NF has the following cables:

The length of the cables suggests that the Nightjar SST-ST50NF is targeted at full-size system cases, unlike the Enhance. However, while the selection of connectors is good, the CPU cable may turn out to be too short to be hidden behind the mainboard’s mounting plate.


The load capacity of the most important +12V rail equals that of the lower-wattage Seasonic. However, those 44 watts that the Nightjar SST-ST50NF cannot deliver across the +12V rail match the typical load on the other rails, so that’s not a shortcoming.

The load capacity of the other power rails is as high as that of the Enhance, yet the maximum load on each rail (+3.3 and +5 volts) is only 18 amperes as opposed to the other PSUs’ 20 amperes.

The Nightjar SST-ST50NF has the lowest 80 PLUS certification in this review. It is Bronze. However, its predecessor with basic 80 PLUS certification was as efficient as 90% through a larger part of the load range.

UPS Compatibility

Working with our APC SmartUPS SC 620, this PSU was stable at loads up to 380 watts when powered by the mains and could switch to the UPS’s batteries at a load of 290 watts.

Cross-Load Voltage Stability

The manufacturer claims that the Nightjar series PSUs keep their voltages within 3% of the required levels and our measurements almost agree with that claim.

Like with the previous PSUs, we can see no problems about the +12V and +5V voltages. They are always within 2% of the required levels.

And like with the previous products, the +3.3V rail is the least stable of all. This voltage can be up to 5% off the necessary level. On the other hand, it is indeed within 3% in the typical load range. In fact, the Nightjar SST-ST50NF is the best of the four PSUs in terms of the +3V voltage at typical loads.

Output Voltage Ripple

The output voltage ripple isn’t strong but there are occasional spikes above the permissible limits on the +5V and +12V rails.

The same goes for the low-frequency voltage ripple, but the occasional spikes aren’t that high here.

Efficiency and Power Factor

The Nightjar SST-ST50NF was 84.9%, 88.9% and 88.7% efficient at the reference loads of 20%, 50% and 100%. This confirms its 80 PLUS Bronze certification. The PSU just lacks a little at 20% load to meet the Silver requirements.

The peak efficiency of 89.9% was achieved at a load of 286 watts. The Nightjar SST-ST50NF couldn’t hit 90% at any point of the graph.

The power factor is about 99%, which is an excellent result.

Standby Source

As expected, the standby source is okay, although its voltage is almost 3% higher than necessary at the minimum load. That’s more than with the other PSUs, but within the requirements of the industry standard.


Based on the oldest platform among the four tested PSUs, the Nightjar SST-ST50NF is still quite a competitive product. It delivers stable voltages and features an overheat indicator. However, it is inferior to its younger opponents in terms of efficiency and output voltage ripple.

Kingwin Stryker STR-500

We tested Kingwin PSUs before but it’s the first time we have a fanless model from this brand.

The Stryker STR-500 comes in a rather large box that lacks a carry handle. There is a photo of the product and a list of its features on the front side.

The back of the box shows another photo of the PSU and announces one of its most exciting features.

The manufacturer claims that this PSU can be “overclocked” to an output power of 600 watts while remaining as efficient as 80 PLUS Gold (it is Platinum-certified at its default parameters).

Besides a mains cord and fasteners, the accessories to this PSU include a user manual (which is practically useless since it has no information about fanless PSUs) and a pouch for detachable cables.

Exterior Design

Like the Silverstone, the Kingwin Stryker STR-500 follows the best traditions of passively cooled PSUs. It has a heat-spreading aluminum top whereas the rest of the case is made of conventional steel painted a rough dark paint.

The side panels are perforated for ventilation, like those of the Silverstone model. The Kingwin doesn’t have the cute indicators of the Silverstone, though. It only has a mains connector and an On/Off switch.

Circuit Design

The LLC marking of the PCB indicates that the actual maker of the PSU platform is Super Flower. We know this manufacturer by NZXT’s Gold-certified PSUs.

The massive top panel, which serves as a heatsink, has fewer holes than its counterpart in the Silverstone Nightjar.

The large heatsinks hide the components of the PSU from our sight.

However, we can spot a number of common features with the Gold-certified products from NZXT (i.e. the Golden Green series from Super Flower) like the same position of the DC-DC converters, daughter card and many other components.

The PSU employs capacitors from United Chemi-Con.

Cables and Connectors

The Kingwin Stryker STR-500 is half-modular. Its main cables are fixed while the others are detachable. It’s equipped with the following cables and connectors:

Included with the PSU are:

The PSU offers enough connectors and its cables are sufficiently long. Take note of the four graphics card connectors: you don’t have to use any adapters to power a multi-GPU configuration built out of two graphics cards with two power connectors each.

The modular system is handy and resembles the one of the NZXT HALE90:

Each of the PSU connectors has all the available voltages.

But the modular cables only use those pins which are necessary for their power connectors. It means that you can plug any cable into any of the PSU sockets without any risk.

As opposed to the Kingwin Lazer LZ-850 which has similar connectors, the fanless Stryker STR-500 doesn’t highlight them.

Overall, the cables of this PSU seem to be the handiest among the four products included into this review.


The Kingwin’s specs are similar to those of the Seasonic’s except for the total wattage (500 instead of 460 watts) and the load capacity of the +12V rail (41.5 instead of 38 amperes).

The Kingwin is certified for the 80 PLUS Platinum standard.

We also checked out the manufacturer’s claim about “overclocking” this PSU to an output power of 600 watts. We had a load up to 588 watts on the +12V rail and a load of 120 watts on the +3.3 and +5V rails combined.

UPS Compatibility

Working with our APC SmartUPS SC 620, this PSU was stable at loads up to 407 watts when powered by the mains but could not switch to the UPS’s batteries even at 280 watts. That’s the worst result in this review.

Cross-Load Voltage Stability

First we tested the PSU at its specified output power of 500 watts.

The +12V voltage is no more than 2% off in the typical load range. The +5V voltage is within 3% of the required level. The +3.3V voltage can deflect by up to 4% when the computer is idle.

When the PSU is “overclocked” to 600 watts, its voltages are just as stable as at 500 watts.

Output Voltage Ripple

Since this test depends on the output power, we carried it out at the PSU’s default 500 watts and in the overclocked 600W mode.

The high-frequency voltage ripple doesn’t change depending on the operation mode and meets the requirements of the industry standard. The Stryker STR-500 is inferior to the Seasonic X-460 in this test, though.

The low-frequency ripple doesn’t depend on the operation mode, either. It is within the norm, too.

Efficiency and Power Factor

This test was also carried out in the PSU’s default and overclocked operation modes. The 500W mode comes first:

The efficiency is 92.4%, 93.1% and 91.3% at the reference loads of 20%, 50% and 100%. This agrees with the 80 PLUS Platinum requirements this model is certified for. The peak efficiency of 93.3% was achieved at a load of 320 watts.

And now the overclocked mode:

The PSU is 91.9%, 92.9% and 90.7% efficient at the loads of 20%, 50% and 100% now. In fact, this is not Gold but Platinum again. Just an excellent performance!

The power factor is about 98% at high loads, which is but slightly lower than the best implementations of active power factor correction.

Standby Source

The standby voltage is no more than 2% off the required level.


The Kingwin Stryker STR-500 features impressive efficiency, very high wattage (for a fanless model) and handy cables. It doesn’t seem to have any downsides, except for its high price. But we guess a silent Platinum-certified 600-watt PSU just can’t be cheap.